/*******************************************************************************
 * Copyright 2006, 2017 Jerry Huxtable, Martin Davis
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * This file was semi-automatically converted from the public-domain USGS PROJ source.
 */
package org.locationtech.proj4j.proj;

import org.locationtech.proj4j.ProjCoordinate;
import org.locationtech.proj4j.util.ProjectionMath;

public class NellHProjection extends Projection {

	private final static int NITER = 9;
	private final static double EPS = 1e-7;

	public ProjCoordinate project(double lplam, double lpphi, ProjCoordinate out) {
		out.x = 0.5 * lplam * (1. + Math.cos(lpphi));
		out.y = 2.0 * (lpphi - Math.tan(0.5 *lpphi));
		return out;
	}

	public ProjCoordinate projectInverse(double xyx, double xyy, ProjCoordinate out) {
		double V, c, p;
		int i;

		p = 0.5 * xyy;
		for (i = NITER; i > 0 ; --i) {
			c = Math.cos(0.5 * xyy);
			out.y -= V = (xyy - Math.tan(xyy/2) - p)/(1. - 0.5/(c*c));
			if (Math.abs(V) < EPS)
				break;
		}
		if (i == 0) {
			out.y = p < 0. ? -ProjectionMath.HALFPI : ProjectionMath.HALFPI;
			out.x = 2. * xyx;
		} else
			out.x = 2. * xyx / (1. + Math.cos(xyy));
		return out;
	}

	public boolean hasInverse() {
		return true;
	}

	public String toString() {
		return "Nell-Hammer";
	}

}
